I say get together and meet regardless of the number.
As you know, we've had many GTG's in So. Cal., and the number of people attending has ranged from more than 2 dozen to maybe 6 guys. They're all fun. With smaller numbers, you get to sit down and really talk to each other, like over lunch or even a cup of coffee.
I've even met one or two members separately for dinner, lunch, had them over to my house, went on a picnic with one guy and his wife and kids.
It's just a great way to spend some time with others who love to talk about their cars. And you know with me, I can talk and talk and talk for hours about only two things: my dog and my Mercedes!
:p